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Reticulo-endothelial macrophages are central for the regulation of iron homeostasis, thanks to their ability to recycle red blood cell-derived iron. Macrophages are also key innate immune cells which exhibit remarkable functional plasticity. These two roles are tightly interconnected: on the one hand, macrophage polarisation dictates the expression of iron-regulated genes and determines cell iron handling; on the other, iron availability affects immune effector functions. Recent observations support a role for free haem and iron in shaping macrophage plasticity towards an M1-like pro-inflammatory phenotype. These findings have implications for the pathophysiology of sickle cell disease, hallmarked by haemolysis and elevated circulating haem and iron, as well as for the tumour microenvironment, characterised by haemolytic red blood cell extravasation and iron-loaded macrophages. Consistently, haem scavenging suppresses the pro-inflammatory profile of macrophages, reducing chronic inflammation in sickle cell disease, whereas nanoparticle-mediated iron delivery to the tumour microenvironment elicits pro-inflammatory macrophages with tumour killing properties, thus delaying tumour growth. This line of research paved the way for the therapeutic modulation of macrophage plasticity achievable through the application of different iron sources or scavengers/chelators according to the desired beneficial effect.

Francisella tularensis is a gram-negative bacterium that can cause gastrointestinal or oropharyngeal tularemia in humans from ingestion of contaminated food or water. Despite the potential for accidental or intentional contamination of foods with F. tularensis, there are no techniques currently available to detect this organism in specific food matrices. In this study, a macrophage cell culture system is combined with real-time PCR to identify F. tularensis in food matrices. The method utilizes a mouse macrophage cell line (RAW 264.7) as host for the isolation and intracellular replication of F. tularensis. Exposure of macrophages to F. tularensis-contaminated food matrices results in uptake and intracellular replication of the bacteria, which can be subsequently detected by real-time PCR analysis of the DNA released from infected macrophage cell lysates. Macrophage monolayers were exposed to infant formula, liquid egg whites, and lettuce contaminated with varying quantities of F. tularensis. As few as 10 CFU/ml (or CFU per gram) F. tularensis was detected in infant formula and lettuce after 5 h postinfection. As few as 10 CFU/ml F. tularensis was detected in liquid egg whites after 18 h postinfection. Intracellular F. tularensis could also be isolated on Mueller-Hinton medium from lysates of macrophages infected with the bacteria in infant formula, liquid egg whites, and lettuce for subsequent confirmatory identification. This method is the first to successfully identify F. tularensis from select food matrices.

In this paper we consider an interaction between a monoclonal tumor and the macrophages, which show a prey-predator structure. This model is analyzed with fuzzy initial values, where the concept of generalized differentiability is used. The graphical solutions for the problem show us interesting results comparing it with the differential equation model.

We investigated the influence of nutritional conditions on histological changes in melano-macrophage (MM) accumulation in the kidney caused by long-term starvation. These data were used to determine nutritional indices for olive flounder, Paralichthys olivaceus (Temminck and Schlegel). Experimental groups were established: control, fed and starved. All fish were fed daily with commercial feed at 1–3% of their total body weight for 2 weeks before the start of the experiment (initial control). The control group received feed at 1–3% of their total body weight and the fed group received feed ad libitum, while the starved group fasted throughout the experiment. Ten fish were removed from the initial control at the start of the experiment and each of the three groups every 4 weeks during the 12 weeks of the experiment to examine to investigate kidney MM accumulation. Kidney MMs with dark brown pigment were randomly distributed in the kidneys of starved fish, increasing rapidly after week 4, while deposition levels remained low throughout the experiment in the control and fed groups. These results suggest that catabolic tissue breakdown is a major factor contributing to the formation of pigments within MMs. These results suggest that the degree of MMs deposition in the kidney can be used as alternative indicators to identify starvation in wild and cultured olive flounder.

Two experiments were conducted to study the interaction between dietary lutein and fat levels in broiler chicks hatched from lutein depleted (Experiment I) and repleted (Experiment II) eggs. In both experiments, a 2 x 3 factorial arrangement of treatments resulted in six dietary treatments (fat at 3% and 6% and lutein at 0, 25 and 50 mg/kg feed) that were fed for 23 days to 18 birds per treatment (in three replications). In Experiment I, the anti-dinitrophenyl-keyhole-lympet-hemocyanin (anti-DNP-KLM) serum antibody response at day 22 and macrophage phagocytotic index at day 17 did not differ among treatment groups (p > 0.05). The concavalin A and phytohaemagglutinin-P lymphocyte proliferation index at day 19 was greater in birds fed 50 mg of lutein and 3% fat than in birds fed all other diets (p < 0.05). Independent of the level of dietary fat, dietary lutein increased macrophage (day 23) nitrite production measured 46 h after in vitro stimulation with LPS (p < 0.05). Among the birds fed lutein at 25 or 50 mg/kg feed, birds fed 3% fat had higher LPS-induced nitrite production compared to the birds fed 6% fat after 46 (p = 0.014) or 70 h (p < 0.001). In Experiment II, macrophage nitrite production was measured at 54 h after LPS stimulation on days 11, 15, 19 and 23. An interaction between dietary lutein and fat levels on nitrite production was observed on day 19 (p = 0.012), where macrophages from birds fed 0 mg lutein and 3% fat had the highest nitrite production (p = 0.012). Macrophages from birds fed lutein at 25 and 50 mg/kg diet and 3% fat had higher (p = 0.012) nitrite production than birds fed 6% fat. Thus, in birds hatched from lutein deplete and replete eggs, modulation of macrophage nitrite production by lutein is dependent on the level of dietary fat.

Previous reports by others establish that particle surface area is related to a change in macrophage function as measured by the ability to clear particles from the alveolar spaces. However, for nanoparticles the relation may not be strictly due to surface chemistry: The cumulative projected area of the particles may reflect the degree to which the inner or outer surface of the macrophage is shielded from other objects or molecules. We apply this alternative interpretation to in vitro measurements of macrophage uptake of 26-nm-diameter fluorescent beads and to in vivo data presented in a classic inhalation toxicology paper on nano-sized TiO2 particles. In their paper, Oberdörster et al. (Environ. Health Perspect. 102[suppl. 5]:173-179, 1994) reported that following inhalation exposure to 20-nm or 250-nm TiO2 particles, the half-times for alveolar clearance of polystyrene test particles were proportional to square centimeters of TiO2 particle surface per million macrophages; macrophage toxicity from TiO2 particle surface was assumed to be the cause of the decrease in the clearance rate of polystyrene test particles. When TiO2 particle projected area was incorporated into the in vivo macrophage dosimetry calculations, particle projected areas ranged in value from covering only a fraction (0.1) of the macrophage surface to covering the cell surface 4 times over. The observed decrease in macrophage mediated alveolar clearance of polystyrene test particles was directly related to the potential for TiO2 particles to mask the surface of the macrophage-a possibility that was visualized in vitro with confocal laser scanning microscopy.

Aims To develop a rapid detection procedure for Listeria monocytogenes in infant formula and lettuce using a macrophage-based enrichment protocol and real-time PCR. Methods and Results A macrophage cell culture system was employed for the isolation and enrichment of L. monocytogenes from infant formula and lettuce for subsequent identification using real-time PCR. Macrophage monolayers were exposed to infant formula and lettuce contaminated with a serial dilution series of L. monocytogenes. As few as approx. 10 CFU ml−1 or g−1 of L. monocytogenes were detected in infant formula and lettuce after 16 h postinfection by real-time PCR. Internal positive PCR controls were utilized to eliminate the possibility of false-negative results. Co-inoculation with Listeria innocua did not reduce the L. monocytogenes detection sensitivity. Intracellular L. monocytogenes could also be isolated on Listeria selective media from infected macrophage lysates for subsequent confirmation. Conclusions The detection method is highly sensitive and specific for L. monocytogenes in infant formula and lettuce and establishes a rapid identification time of 20 and 48 h for presumptive and confirmatory identification, respectively. Significance and Impact of the Study The method is a promising alternative to many currently used q-PCR detection methods which employ traditional selective media for enrichment of contaminated food samples. Macrophage enrichment of L. monocytogenes eliminates PCR inhibitory food elements and contaminating food microflora which produce cleaner samples that increase the rapidity and sensitivity of detection.

Description of macrophage activation is currently contentious and confusing. Like the biblical Tower of Babel, macrophage activation encompasses a panoply of descriptors used in different ways. The lack of consensus on how to define macrophage activation in experiments in vitro and in vivo impedes progress in multiple ways, including the fact that many researchers still consider there to be only the two types of activated macrophages often termed M1 and M2. Here we describe a set of standards for the field encompassing three principles: the source of macrophages, definition of the activators, and a consensus collection of markers to describe macrophage activation, with the goal of unifying experimental standards for diverse experimental scenarios. Collectively, we propose a common framework for macrophage activation nomenclature.

High-throughput (HTP) technologies enabling the simultaneous measurement of thousands of genes, proteins, and metabolites offer new opportunities for understanding the complex mechanisms underlying physiology, health, and disease. Mining these large “omics” datasets (transcriptomics, proteomics, and metabolomics) has required addressing issues such as high dimensionality of the data, experimental variability, noise, and low sensitivity of the methodologies. Numerous approaches have been developed to handle these issues and to utilize these datasets to generate meaningful biological insights. This chapter describes the types of omics measurements that have been performed on mammalian macrophage cells, methods, and tools for their analysis, and examples of insights gained in macrophage biology.

Macrophages are an essential part of our immune system and one of the well-known cells in biology. However, despite its importance its usual behaviour and moving rules are mostly unknown due to the lack of observatory data for the macrophages. An experiment was conducted in an attempt to obtain new data by observing the macrophages in a living rat and produced a couple of movies. Our objective is to exploit these results to develop a simulator that is able to reproduce the moves of a macrophage population. After the movie analysis, we identified a few characteristics to implement into a first simple simulator. Although its performance is very limited, it represents a first step for further research of understanding macrophages.

Macrophage centres have been considered as a potentially useful indicator of fish health. In this histological work we tested this hypothesis with macrophage centres (MCs) in the spleen, the liver and the hematopoietic part of the kidney of two common freshwater fish species in Finland, perch ( Perca fluviatilis ) and roach ( Rutilus rutilus ). Samples were collected over 5 seasons from a system of 4 lakes providing a gradation in water quality. The mean number of MCs/mm 2 and the area covered (μm 2 /mm 2 ) by them differed between individual fish, species, organs, and lakes, with interactions amongst these factors. Hemosiderosis was recorded from the spleen and liver of both fish species; amounts differed between species of fish, organs, and lakes. None of the observed patterns agreed with rankings of water quality, and we conclude that macrophage centres have limited usefulness as indicators of pollution.

Although already evident from the earliest days of macrophage research, the diversity of macrophage distribution, morphology, and function continues to attract immunologists interested in their role in physiology and disease. Contemporary tools of cellular and molecular analysis have begun to unravel their versatile and adaptable gene expression, the result of differentiation and modulation by their environment. In this brief account, I outline the history of my personal involvement in this subject.

The aim of this work was to evaluate the effect of broiler breeders' age and yeast wall (YW) levels on broilers' performance and macrophage activitys. The experiment consisted in a completely randomized design and a 2 X 5 factorial arrangement and two controls of two broiler breeders age (34 and 57 weeks of age) and five YW levels (zero, one, two, three or four kg of YW/ton of diet). They received sorghum diet compared to a control corn/soybean meal diet. The age of the broiler breeders influenced the performance, but did not affect macrophage activity. At 34 weeks age broiler breeders' progeny, all diets were similar considering the average weight. For 57 weeks age broiler breeders' progeny, at 21 days, only average weight of sorghum diet supplemented with 4 kg/ton was similar to corn diet results. The optimum level of YW for maximal macrophage activity was 2.06 kg/ton of meal.

Summary: The Macrophage Pathway Knowledgebase (MACPAK) is a computational system that allows biomedical researchers to query and study the dynamic behaviors of macrophage molecular pathways. It integrates the knowledge of 230 reviews that were carefully checked by specialists for their accuracy and then converted to 230 dynamic mathematical pathway models. MACPAK comprises a total of 24 009 entities and 12 774 processes and is described in the Cell System Markup Language (CSML), an XML format that runs on the Cell Illustrator platform and can be visualized with a customized Cytoscape for further analysis. Availability: MACPAK can be accessed via an interactive web site at http://macpak.csml.org. The CSML pathway models are available under the Creative Commons license. Contact: masao@hgc.jp

Background In an effort to better understand the molecular networks that underpin macrophage activation we have been assembling a map of relevant pathways. Manual curation of the published literature was carried out in order to define the components of these pathways and the interactions between them. This information has been assembled into a large integrated directional network and represented graphically using the modified Edinburgh Pathway Notation (mEPN) scheme. Results The diagram includes detailed views of the toll-like receptor (TLR) pathways, other pathogen recognition systems, NF-kappa-B, apoptosis, interferon signalling, MAP-kinase cascades, MHC antigen presentation and proteasome assembly, as well as selected views of the transcriptional networks they regulate. The integrated pathway includes a total of 496 unique proteins, the complexes formed between them and the processes in which they are involved. This produces a network of 2,170 nodes connected by 2,553 edges. Conclusions The pathway diagram is a navigable visual aid for displaying a consensus view of the pathway information available for these systems. It is also a valuable resource for computational modelling and aid in the interpretation of functional genomics data. We envisage that this work will be of value to those interested in macrophage biology and also contribute to the ongoing Systems Biology community effort to develop a standard notation scheme for the graphical representation of biological pathways.

The success of regenerative materials is dependent on the ability to elicit cell interactions. Cell–material interactions, both desired and undesired, are dictated by the physical properties of the material. Previous research has focused on surface chemistry and feature size of biomaterials. The role of shape, in particular the ability of cells to recognize and respond to shape, has not been determined. This is primarily due to the limited availability of techniques to produce materials with features of controlled and varied morphologies. To this end, we have created a diverse collection of novel polymer micro- and nano-particle shapes and studied their phagocytosis by macrophages. The macrophage immune response to biomaterials is a formidable obstacle in delivery and integration of materials for successful tissue regeneration, engineering, and drug delivery. The results show that particle shape, from the point of view of the macrophage, profoundly impacts phagocytosis, more than particle size and independent of surface chemistry. We can use this understanding to design material features that will direct desired macrophage response and, in the future, study the effects of shape on other cell functions. This work demonstrates the importance of shape in the design of biomaterials and its influence on cell–material interactions.

The effects of salinity adaptation and ration size on macrophage phagocytosis were assessed in black sea bream (Mylio macrocephalus) juveniles. Salinity had no effect on phagocytosis in fish that were fed a 10% ration size. Reducing ration size from 10 to 5% resulted in a significant reduction in splenic and pronephric macrophage phagocytosis of fish adapted to hyper-(33 p.p.t.) and hypo-osmotic (6 p.p.t.) salinities. The fish that were adapted to an iso-osmotic salinity (12 p.p.t.) and fed a 5% ration size were able to maintain macrophage phagocytic activity at levels comparable to those of fish that were fed a 10% ration size. It is proposed that the adaptation of sea bream to an iso-osmotic medium is beneficial in that it stimulates the immune response through activation of macrophage phagocytosis.

Several studies have tackled the evaluation of the biocompatibility of nanomaterials in cell and tissue. Nonetheless to date, a quantitative technique for the assessment of the total intracellular nanocarrier dose administered has not been introduced. In this paper we develop two rapid and sensitive assays for the measurement of internalized nanomaterials in macrophages to be applied as vehicular carriers for drug delivery and contrast imaging applications. Five commercially available polystyrene particles with different diameters (from 20 to 1000 nm) were used and imaged by using a 3dimensional confocal imaging techniques. The two proposed assays are: 'volumetric' assay which evaluate the spherical volume of internalized particles and 2) 'max-flat' assay which evaluate the total differential area between cells and internalized particles. These two assays were then compared to a reference method. Among these three assays, the 'max-flat' assay was found to be the most reliable and accurate to quantify and investigate the total content of internalized nanomaterials. The 'max-flat' assay also allowed for a 3dimensional subcellular investigation of the adaptation and localization mechanisms between cytoskeleton and internalized materials, which may help to further increase the selectivity and delivery of active and passive biopolymers. Therefore, we believe that the here presented assays could become a useful tool to address many biomaterials questions, especially where the key issue is the quantitative assessment of dose effect issues related to the size-dependence response of nanomaterials.

In the spirit of the Leiden Conferences, the first Keystone Meeting on Macrophage Biology brought together scientists from a wide range of disciplines. Precisely because macrophages perform such diverse functions, this meeting had an extraordinarily broad scope. While this was exhilarating to experience, it is impossible to report in full. We have highlighted, therefore, only a few themes and have had to omit many outstanding presentations that fell outside of these boundaries.

This conversation is about research highlighted in the Editors' Choice summary titled, "Macrophages Go Back to School." The highlighted articles are T. Hagemann, T. Lawrence, I. McNeish, K. A. Charles, H. Kulbe, R. G. Thompson, S. C. Robinson, F. R. Balkwill, "Re-educating" tumor-associated macrophages by targeting NF-κB. J . Exp . Med . 205 , 1261-1268 (2008), and C. H. Y. Fong, M. Bebien, A. Didierlaurent, R. Nebauer, T. Hussell, D. Broide, M. Karin, T. Lawrence, An antiinflammatory role for IKKβ through the inhibition of "classical" macrophage activation. J . Exp . Med . 205 , 1269-1276 (2008). (Length: 11 min; file size: 5.00 MB; file format: mp3; location: http://podcasts.aaas.org/science_signaling/ScienceSignaling_080715.mp3 )

High-throughput microarray data are extensively produced to study the effects of different treatments on cells and their behaviours. Understanding this data and identifying patterns of groups of genes that behave differently or similarly under a set of experimental conditions is a major challenge. This has motivated researchers to consider multiple methods to identify patterns in the data and study the behaviour of hundreds of genes. This paper introduces three methods, one of which is a new technique and two are from the literature. The three methods are cluster mapping, Rank Products and SAM. Using real data from a number of microarray experiments comparing the effects of two very different products that can activate macrophage tumoricidal activity we have identified groups of genes that share interesting expression patterns. These methods have helped us to gain an insight into the biological problem under study.

The functional heterogeneity of macrophages based on anatomical localization and receptor expression as well as their versatile way through which they react to different stimuli makes them key players in many processes of the body. To stimulate or downregulate their functions in therapeutic ways using their extremely efficient phagocytosis capacity, one has to consider that they are often located at sites that are hard to reach. Local administration of drugs is therefore often the method of choice whereby liposomes seem to be an ideal vehicle through their versatility and relative ease of handling, as well as their efficient uptake by macrophages. Especially the use of the macrophage suicide technique has enabled the study of many functions of the macrophage. An overview is given of the many routes that can be used to reach the macrophage at different sites and the effects this has on the function of the cell.